The invention relates in the first place to a method for cementing in the manufacture of double-pane insulating glass units in which one pane is separated by a framelike spacer from a second pane, and the pane package thus formed is cemented by injecting a cement into an interspace limited by the outside of the spacer and the pane edges projecting beyond the spacer, employing at least two injecting nozzles for the cement.
Double-pane insulating glass is thermally and acoustically insulating. This is due to the air enclosed between the two glass panes and the spacer frame. In the finished double-pane insulating glass, the sides of the panes that face each other are not accessible. In order to avoid a dimming of the panes from the inside, the dew point of the enclosed air is lowered to such an extent that at the usually occurring degrees of coldness the temperature cannot drop below this dew point.
In such double-pane insulating glasses, the initially mentioned air interspace is essentially sealed with relation to the outside. The air is dried by means of a hygroscopic material. This material may be contained in a hollow spacing frame and may act upon the enclosed air through recesses in the spacing frame. Minor leaks of the pane cement can likewise be compensated by this material.
It is known to connect first the spacer with the panes by a cement applied to the sides of the spacer that face the panes, the final pane connection being brought about by a second cement injected into the interspace described which is limited by the outside of the spacer and the pane edges projecting beyond the spacer. These manufacturing processes must predominantly be carried out by hand, permitting therefore only a small degree of mechanization and requiring furnaces for hardening the cement injected into the interspace. Besides, waste may readily be produced in such processes if the panes shift and the cement applied to the frame stains the panes.
Of course, cements have recently been employed which do not require a separate cementing of the spacer with the panes, and which therefore permit a higher degree of mechanization. In particular, prior art does not include thermoplastic cements which connect the panes with the spacer so quickly that special furnaces for hardening the cement are not needed.
Of course, these novel cements, which permit a particularly high degree of mechanization, require the use of extruders, from the nozzles of which the cement is discharged in a hot state, in which process temperatures of about 170.degree.C occur. The cement cools off rapidly. In this instance, it should be noted that the hot cement does not combine with the same cement which has already cooled off. Since the entire interspace cannot be filled with cement all at once, special measures, possibly the application of high pressures, were hitherto required, so as to establish an intimate connection at the boundaries of the first injected cement portions with those injected later. These measures, and especially the application of high pressures, could, of course, hitherto not be carried out in a largely mechanized manufacturing process.